[Halld-tagger] tagger energy tables in ccdb are up to date

[Daniel Sober]

A footnote to Richard's last sentence ("... unless a large change in the
tagger magnetic field setting is required.")

Remember that the effects of changes in the field have already been
calculated using the field maps at 0.75T (6 GeV) and 1.7T (13.6 GeV),
and they are very small, as documented on my web page,
https://userweb.jlab.org/sober/HallD/mapping

Figure 8 ("Error in energy ...") of Mapping_analysis.pdf shows that
1)  at 6 GeV, the maximum energy error incurred by using the scaled 12 GeV
field map is < 0.8 MeV (< 0.2 MeV in the Micrroscope region).
2)  at 13.6 GeV, the maximum energy error is < 3.5 MeV (< 2 MeV in the
Microscope region).

For the (utopian) possibility of energies substantially above 12 GeV, I
have addressed the possibility of improving the energy calculation
in the note E0_interpolation.pdf posted on the same web page
("Interpolation between the field maps")

Dan

On Tue, Nov 21, 2017 at 9:18 AM, Richard Jones <richard.t.jones at uconn.edu>
wrote:

> Dear colleagues,
>
> At the photon beam meeting yesterday, the question came up whether the
> tagger energy tables in ccdb reflect the latest raytracing results from Dan
> Sober. I communicated with Dan, and he confirmed that the tables from
> January 2017 that I received from him earlier this year are the most
> up-to-date results he has produced. These are the ones in Counterbounds2017
> that are posted on the wiki.
>
> I then compared all of these with what is in ccdb at mysql://
> ccdb_user at hallddb.jlab.org/ccdb
> All channels agree with Dan's table within a precision of 6 sig figs. This
> single set of values currently applies to all runs, both real data and mc.
> They are automatically scaled by the electron beam energy, which is in
> another ccdb table, so they are not expected to vary much from one run
> period to another, unless a large change in the tagger magnetic field
> setting is required.
>
> -Richard Jones
>
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